Reverse osmosis membranes are becoming increasingly popular for water purification applications that require high salt rejection such as brackish and seawater desalination. However, due to fouling by microorganisms, they have been unable to realize their full potential as of yet. Biofouling leads to the use of higher operating pressure, more frequent chemical cleaning, and shorter membrane life. This paper reviews the causes, consequences and control of biofouling in RO membranes used for seawater desalination. After a brief introduction, the fundamentals of biofouling are discussed in some detail: biofilm formation, role of EPS, and sequence of events leading to biofouling. This is followed by a section on consequences of biofouling on membrane processes with particular emphasis on water permeability and salt rejection. The mechanisms of performance degradation are discussed in some detail for both of these parameters. The last section of this paper reviews the different antifouling strategies that have recently gained more attention with special emphasis on membrane surface modification. A brief conclusion with some recommendations and suggestions is presented at the end of the article.